Sunday, November 30, 2008

Making sure your home is not an energy sink - II

Science Alert | In the first part, I mentioned how some appliances use a considerable amount of energy when not in use. For example, my son recently installed a 5-star split-system air-conditioner. It draws 10 watts on standby.

If we do the calculations, 10 W (watts) for 24 hours a day, 365 days a year comes to 88 kWh (kilowatt hours) per year.

Now let’s work out its likely usage when operating. Say we have 20 hot days a year when the system is running flat out for 8 hours. Let’s conservatively assume that running flat out, it draws 550 watts. The sum of 550 watts for 8 hours for 20 days comes to 88 kWh per year.

This 5-star-rated appliance uses as much energy on standby as doing its job. Systems like this should be installed with a switch so they can be turned off completely for most of the year.

One last point. I have only considered domestic hot water, lighting, cooking and domestic appliances. I have not mentioned space heating, transport, holidays, the workplace and the energy in all the goods and services we buy.

That comes in the next exciting episode!